The objective of this project is to develop a model of chronic hypertension in dogs exposed to a combination of inhibitory behavioral stress conditioning and increased sodium intake. Inhibitory behavioral stress conditioning has been shown to result in progressive elevations in total peripheral resistance but not cardiac output during periods of hours of experimental stimulation. Respiratory inhibition has been shown in these experiments to alter plasma electrolyte balance, which may increase circulating levels of aldosterone and decrease renal excretory functions. Dogs will be exposed to (a) stress conditioning in a context of dietary sodium restriction, (b) salt loading without stress conditioning, or (c) stress conditioning plus salt loading over periods of up to 20 weeks. Chronic adaptations of blood pressure and associated physiological functions will be monitored continuously under these conditions.